Syringe with needle and method of attaching same

ABSTRACT

A hypodermic syringe with a tapered adapter surrounded by an internally threaded locking sleeve. A needle hub with at least one locking ear is threaded partway onto the tapered adapter and thereafter longitudinally staked to separate pressure contact between the needle ear and thread during storage.

BACKGROUND

U.S. Pat. No. 4,027,669 describes a thermoplastic syringe barrel with anintegral tapered adapter surrounded by an internally threaded lockingsleeve. This sleeve is longitudinally slotted to aid in strip ejectionfrom a mold during its manufacture.

Integral locking sleeves that are strip ejected are more economical tomanufacture than separately molded sleeves which must be subsequentlyattached to a syringe barrel, as described in U.S. Pat. Nos. 3,469,581and 3,542,024. However, the threads in such strip ejection sleeve havelimited height and tapered rear surfaces to prevent substantial damageto the threads during strip ejection. Such threads have sufficientholding power to grip the needle hub's ears when assembled by a nurse orphysician immediately prior to use. This is because there is no longterm distorting pressure between the hub ears and threads.

Most disposable thermoplastic syringes are sold today with a needlepreattached. The needle hub's ears and threads of the locking sleeve maybe in high pressure abutment for several months during shipping,storage, etc. prior to use. This can cause some relief in the holdingpower of the threads on the needle hub ears.

In addition, strip ejected screw threads of limited holding power haveproblems with machine assembly of the needle to the syringe. If theneedle is longitudinally jammed (without screwing) onto the taperedadapter to snap the hub's ears behind the threads, this causes somedamage to the threads, reducing their already limited holding power.Machine assembly of the needle to the syringe with a screwing motion tofirmly seat the needle on the tapered adapter sometimes causes the hubears to snap out from behind the threads and form a scar or damage inthe threads which can reduce the thread's holding power.

Threads in integral locking sleeves on syringes can be made with agreater height and more stability by unscrewing the syringe barrel andintegral sleeve from its mold rather than using the longitudinal stripejection process. However, such unscrewing process requires expensivemechanisms on the mold which substantially increase manufacturing cost.

SUMMARY OF THE INVENTION

The above problems with integral strip ejected locking sleeves in athermoplastic sleeve have been overcome by the present invention. Thisinvention includes screwing a needle hub with protruding ears partwayinto a locking sleeve, and thereafter longitudinally staking the hub tofirmly seat it onto the tapered adapter and space the hub's projectingears from a rear surface of the sleeve's threads. This relieves abuttingstresses between the threads and hub ears, and also permits very firmassembly of the needle to the tapered adapter by the manufacturerwithout scarring the sleeve's threads.

THE DRAWINGS

FIG. 1 is a side elevational view of the syringe with attached needle;

FIG. 2 is an enlarged fragmentary sectional view of a forward upstandingtip of a syringe barrel showing assembly of a needle hub;

FIG. 3 is a rear end view of the needle hub showing its projecting ears;and

FIG. 4 is a fragmentary schematic view showing the vertical positioningof the hub ear between adjacent threads.

DETAILED DESCRIPTION

In FIG. 1, a syringe barrel 1 has an internally threaded locking sleeve2 surrounding a tapered adapter 3 to which is mounted a needle hub 4.Needle hub 4 is connected to a conventional cannula (not shown) which isencased inside a protector 5. Preferably, locking sleeve 2 has severallongitudinal slots 6 to aid in strip ejection of thermoplastic sleeve 2which is integrally formed with barrel 1.

The relationship of needle hub 4 and sleeve 2 are best seen in FIG. 2.Here the internal threads, represented as 7, are preferably in doublehelical form in that the sleeve has two spiral threads each having itsown lead-in entrance adjacent a forward portion 8 of the sleeve. Thesetwo lead-ins are diametrically opposed on opposite sides of the sleeve2.

Because of the longitudinal strip ejection of the integral thread 7, itssize and rear surface slope structure are limited to permit the stripejection without scarring or damaging thread 7. In a first step of theassembly process, hub 4 is screwed into sleeve 2 until it begins towedge unto tapered adapter 3. An assembly machine performing this screwon step is adjusted so that its screwing motion is not so forceful as tosnap ears 9 and 10 on the hub out from behind threads 7. Thus, duringthis step no damage is done to thread 7.

After the partial assembly by screwing, a second step of longitudinalstaking is accomplished. This involves applying a force of at least 10pounds axial force to firmly wedge the hub 4 onto tapered adapter 3.This staking is done without a screwing motion and causes ears 9 and 10to assume the positions shown in dotted line. This relieves any abutmentpressure between the hub ears and threads during storage.

FIG. 3 shows a rear end view of the needle hub 4 with its protrudingears 9 and 10 that have a considerable width for gripping the sleevethreads over a wide area. The ear width is shown in FIG. 3. Therelationship between adjoining threads and ear width is shownschematically in FIG. 4. Here thread sections 7 and 7a arelongitudinally separated by a distance sufficient to permit longitudinalstaking to a position shown in dotted line without substantial damage tothread section 7a. For the schematic illustration, thread sections 7 and7a are not shown in spiral form as they would be on an internal surfaceof sleeve 2.

The above process for assembling the needle and syringe and itsresulting structure works very well when a double helical thread hasapproximately 8 simulate threads/inch. For purposes of determining thisthread pitch, both helical threads are included.

Even though the needle assembled by the above screwing and subsequentstaking process very firmly attaches the needle to the syringe in theposition shown by dotted line, a nurse or physician can readily removethe needle by a twisting motion for changing needle size, etc., whendesired.

In the foregoing description, a specific example has been used todescribe the invention. However, it is understood by those skilled inthe art that certain modifications can be made to this example withoutdeparting from the spirit and scope of the invention.

I claim:
 1. A syringe and attached needle hub in which the syringe has atapered adapter surrounded by an internally threaded locking sleeve andthe needle hub has at least one laterally protruding ear, wherein theimprovement comprises: a longitudinal spacing between a forward surfaceof the needle hub's ear and a longitudinally aligned rearward surfacearea of a thread on the sleeve, whereby abutting pressure between thethread and needle hub ear are relieved during storage.
 2. A syringe andattached needle hub as set forth in claim 1, wherein the needle hub hasa pair of diametrically opposed ears.
 3. A syringe and attached needlehub as set forth in claim 1, wherein both the needle hub ears andlocking sleeve threads are thermoplastic.
 4. A syringe and attachedneedle hub as set forth in claim 1, wherein the locking sleeve has adouble helic thread with approximately 8 simulate threads per inch basedon both threads.
 5. A method of assembling a needle hub with at leastone laterally protruding ear to a syringe with a tapered adaptersurrounded by an internally threaded locking sleeve, which includes thesteps of:(a) screwing the needle hub partway onto the adapter with theear engaging the threads of the locking sleeves; and (b) longitudinallystaking the needle hub to the syringe adapter to longitudinally separatea forward surface of the needle hub ear from a longitudinally alignedrearward surface of the sleeve's thread.
 6. A method as set forth inclaim 5, wherein the staking force is at least 10 pounds.